can i change a variable from other js?

var trackError : int = 0;

function OnTriggerEnter(other : Collider){
    if(other.tag == "Player"){
        Application.LoadLevel(0);
        trackError=trackError+1;
        print(trackError); 
    }
}   

why always print 1?
second question can i have 2 js and link it each other ? how it works and how to get the variable?

Its printing 1 because you are loading the level from scratch.
If you wish to store a persistent value use PlayerPrefs